1. The Field of the Invention
The present invention is in the field of dental desensitizing compositions used to desensitize a person's teeth. More particularly, the invention relates to substantially solid dental desensitizing compositions and devices in the shape of a dental tray that becomes adhesive when moistened (e.g., by saliva on a user's teeth), as well as methods for their manufacture and use.
2. The Relevant Technology
Tooth sensitivity is a common problem for many dental patients. This sensitivity may result from or be associated with the existence of a cavity, tooth or root fractures, gingival recession, exposed dentin, toothbrush abrasion, bleaching, attrition, erosion, grinding, or trauma from periodontal disease. Tooth sensitivity can become so uncomfortable that it may prevent a patient from eating or drinking certain foods, being outdoors in cold weather, or maintaining good oral hygiene practices. Tooth sensitivity is also a common complaint during dental bleaching regimens. Dental bleaching compositions, which typically comprise a peroxide bleaching agent, can cause tooth sensitivity and pain that, if left untreated, may cause the user to prematurely abort the bleaching process.
To relieve tooth sensitivity, there are currently many non-permanent treatment options available. The most common options include using desensitizing toothpastes, varnishes, gels, and rinses. These products may include, but are not limited to, desensitizing agents such as potassium nitrate, other potassium salts, citric acid, citrates, strontium chloride, stannous fluoride, and sodium fluoride.
Desensitizing dentifrices are a popular treatment option in treating sensitivity. To use desensitizing dentifrices, it is usually recommended that the patient use the dentifrice twice daily. However, results are not immediate. It usually takes an extended period of time (about 1–4 weeks) to be effective and to relieve sensitivity. The main reason for this is that people typically only brush their teeth for about 60 seconds or less, which translates into extremely limited contact time between the desensitizing agent and the person's teeth.
Another treatment involves the use of desensitizing gels that are applied using custom-fitted trays. The process of making a custom-fitted tray generally involves: (1) making an alginate impression of the patient's teeth; (2) making a stone cast or model of the impression; (3) vacuum forming a dental tray from the model, usually from a heated sheet of thin ethyl vinyl acetate (EVA) material, and (4) trimming to exclude gingival coverage. This method results in a tray that is soft and flexible, that is customized to very accurately fit over the patient's teeth, and that is therefore very comfortable to wear. In sum, the process for making a customized tray is time consuming, often taking days or weeks before the customized tray is available to the patient, and the resulting tray can be expensive.
Because of the time and cost associated with customized trays, less time consuming and costly alternatives have been developed. One alternative to customized dental trays is non-customized trays that approximate the shapes and sizes of a variety of users' dental arches. While non-customized dental trays can be used without the need for a professional customization procedure by a dentist, such trays tend to be more bulky and less comfortable than custom-fitted trays. Dental trays that can be self-customized (e.g., so-called “boil and bite” trays) are somewhat more comfortable and better-fitting compared to non-custom trays but less comfortable than trays that are customized by a dentist.
An alternative to the use of dental trays involves placing a flexible dental treatment strip over a user's tooth surfaces, typically for bleaching. Dental strips typically comprise a flexible plastic strip coated with a moist dental gel on the side of the strip facing the user's teeth. To install the strip, a portion of the strip is first placed over the front surfaces of the user's teeth, followed by folding the remainder of the strip around the occlusal edges of the teeth and back against a portion of the lingual surfaces. Like paint-on bleaching compositions, the use of dental strips does not require the user to use a customized or non-customized tray. An advantage of dental strips over paint-on compositions is that strips include a barrier that, at least in theory, protects the moist gel composition from diffusing into the user's mouth.
In reality, because of the generally poor adhesion of dental strips to the user's teeth, coupled with their generally flimsy nature, it is often difficult for the user to maintain the strips in their proper position. Dental strips are prone to slip off the teeth through even minimal movement of the user's mouth, jaw or tongue. Indeed, it is recommended that the user not eat, drink, smoke or sleep while wearing dental strips.
Even if a user successfully maintains the strip in its proper position during the entire treatment time, the flowable gel composition can diffuse into the person's saliva, potentially causing a poor taste in the user's mouth and possibly discomfort to soft oral and throat tissues. The tendency of the gel to diffuse into the user's mouth can be accelerated through even minimal shifts of the dental strip over the user's teeth, with each shift potentially exposing a new portion of the gel that remains adhered to the newly exposed surface of the user's teeth. In some cases, the dental strip can become so dislodged or mangled that it must be removed by the user and replaced with a fresh strip to complete the recommended treatment time. This multiplies the cost and hassle of the dental strip method.
In practical terms, the use of dental strips can greatly inhibit even the simplest of activities that involve movement of the user's mouth or tongue, such as talking, coughing, yawning, smiling, making other facial expressions, or even swallowing (which normally occurs subconsciously throughout the day). Indeed, the time when a person's mouth and tongue are prone to move the least is at night while the person is sleeping. Unfortunately, it is recommended that dental strips not be used while sleeping, presumably to prevent accidental choking on an inadvertently dislodged strip. This only confirms the tendency of conventional dental strips to easily dislodge from a user's teeth.
In view of the foregoing, there is an ongoing need for improved desensitizing compositions, apparatus and methods that are simple and easy to use, that more reliably remain in position over the user's teeth, and that result in less diffusion of desensitizing compositions into a user's oral cavity. Such improvements would be expected to improve or encourage compliance by the user.